let dt = 0.001                        (* Integration step                     *)

let node f_integr (x0, x') = x where  (* Forward Euler integrator             *)
  rec x = x0 -> pre (x +. x' *. dt)
let node b_integr (x0, x') = x where  (* Backward Euler integrator            *)
  rec x = x0 -> (pre x) +. x' *. dt

let node sincos () = (sin, cos) where
  rec sin = f_integr(0.0, cos)
  and cos = b_integr(1.0, -. sin)

let node main () =
  let rec t = 0.0 -> pre t +. dt in
  let (sin, cos) = sincos () in
  match t <= 500.0 with
  | true ->
      (print_float t; print_string "\t";
       print_float sin; print_string "\t";
       print_float cos; print_newline ())
  | false -> ()